'\" et
.TH MLOCK "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
mlock,
munlock
\(em lock or unlock a range of process address space
(\fBREALTIME\fP)
.SH SYNOPSIS
.LP
.nf
#include <sys/mman.h>
.P
int mlock(const void *\fIaddr\fP, size_t \fIlen\fP);
int munlock(const void *\fIaddr\fP, size_t \fIlen\fP);
.fi
.SH DESCRIPTION
The
\fImlock\fR()
function shall cause those whole pages containing any part of the
address space of the process starting at address
.IR addr
and continuing for
.IR len
bytes to be memory-resident until unlocked or until the process exits
or
.IR exec s
another process image. The implementation may require that
.IR addr
be a multiple of
{PAGESIZE}.
.P
The
\fImunlock\fR()
function shall unlock those whole pages containing any part of the
address space of the process starting at address
.IR addr
and continuing for
.IR len
bytes, regardless of how many times
\fImlock\fR()
has been called by the process for any of the pages in the specified
range. The implementation may require that
.IR addr
be a multiple of
{PAGESIZE}.
.P
If any of the pages in the range specified to a call to
\fImunlock\fR()
are also mapped into the address spaces of other processes, any locks
established on those pages by another process are unaffected by the
call of this process to
\fImunlock\fR().
If any of the pages in the range specified by a call to
\fImunlock\fR()
are also mapped into other portions of the address space of the calling
process outside the range specified, any locks established on those
pages via the other mappings are also unaffected by this call.
.P
Upon successful return from
\fImlock\fR(),
pages in the specified range shall be locked and memory-resident. Upon
successful return from
\fImunlock\fR(),
pages in the specified range shall be unlocked with respect to the
address space of the process. Memory residency of unlocked pages is
unspecified.
.P
Appropriate privileges are required to lock process memory with
\fImlock\fR().
.SH "RETURN VALUE"
Upon successful completion, the
\fImlock\fR()
and
\fImunlock\fR()
functions shall return a value of zero. Otherwise, no change is made to
any locks in the address space of the process, and the function shall
return a value of \-1 and set
.IR errno
to indicate the error.
.SH ERRORS
The
\fImlock\fR()
and
\fImunlock\fR()
functions shall fail if:
.TP
.BR ENOMEM
Some or all of the address range specified by the
.IR addr
and
.IR len
arguments does not correspond to valid mapped pages in the address
space of the process.
.P
The
\fImlock\fR()
function shall fail if:
.TP
.BR EAGAIN
Some or all of the memory identified by the operation could not be
locked when the call was made.
.P
The
\fImlock\fR()
and
\fImunlock\fR()
functions may fail if:
.TP
.BR EINVAL
The
.IR addr
argument is not a multiple of
{PAGESIZE}.
.P
The
\fImlock\fR()
function may fail if:
.TP
.BR ENOMEM
Locking the pages mapped by the specified range would exceed an
implementation-defined limit on the amount of memory that the process
may lock.
.TP
.BR EPERM
The calling process does not have appropriate privileges to perform
the requested operation.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIexec\fR\^",
.IR "\fIexit\fR\^(\|)",
.IR "\fIfork\fR\^(\|)",
.IR "\fImlockall\fR\^(\|)",
.IR "\fImunmap\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<sys_mman.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
